[Gamble]

So long story short here. I got this maxnc mill a year ago and it's a piece of ****. Literally motor started on fire, second motor DOA, 3rd motor (consew) died after a few hours. TinyG controller **** the bed. UPS broke it upon arrival. You name it, it's happened.
Anyway. After 4 months I finally got the motor back. I think I have the new tinyg board in there, it's been so long I don't remember. Hooked up to a 24v power supply. Part number: HF240W-SF-24
I took pictures of how the motors and power supply were wired and I kept it all the same when I put it back together
the last owner even put tape and labeled them for me so I'm pretty sure its right.

Plugged it in to test it and the outlet shorted to the plug. Instantly. Doubled checked all the wires and tried again with a extension cord with a circuit breaker on it. Instantly tripped the breaker at the panel, not on the cord.

What could cause this? I know it's got to be a dead short but how do I find out where
I took out my fluke and tested continuity from each side of the 110v plug to ground and they are all open. So nothing obvious. Unless the power supply broke out of nowhere?

[mactec54]

So long story short here. I got this maxnc mill a year ago and it's a piece of ****. Literally motor started on fire, second motor DOA, 3rd motor (consew) died after a few hours. TinyG controller **** the bed. UPS broke it upon arrival. You name it, it's happened.
Anyway. After 4 months I finally got the motor back. I think I have the new tinyg board in there, it's been so long I don't remember. Hooked up to a 24v power supply. Part number: HF240W-SF-24
I took pictures of how the motors and power supply were wired and I kept it all the same when I put it back together
the last owner even put tape and labeled them for me so I'm pretty sure its right.

Plugged it in to test it and the outlet shorted to the plug. Instantly. Doubled checked all the wires and tried again with a extension cord with a circuit breaker on it. Instantly tripped the breaker at the panel, not on the cord.

What could cause this? I know it's got to be a dead short but how do I find out where
I took out my fluke and tested continuity from each side of the 110v plug to ground and they are all open. So nothing obvious. Unless the power supply broke out of nowhere?

Would need to see photos of all the wired parts, but could be the power supply has a short, the power supply will have a fuse inside as well so should be protected

Just power up the Power supply without anything attached to it's output

[Gamble]

Is it safe to keep doing? It was blowing the 100amp breaker in the main that feeds the sub panel

Eh I don’t see a way to upload the pics yet

[mactec54]

Is it safe to keep doing? It was blowing the 100amp breaker in the main that feeds the sub panel

Eh I don’t see a way to upload the pics yet

No it is not safe, did you try the power supply by itself

To post photos hit reply with a quote, then hit go advanced, scroll down, and you will see Manage Attachments, this is where/ how to add photos

[109jb]

Its tripping the 100 amp main in the sub-panel????? Don't you have it running off a breaker within the sub-panel, something like 15 or 20 amp? The main in the sub-panel should not be tripping.

[Gamble]

Its tripping the 100 amp main in the sub-panel????? Don't you have it running off a breaker within the sub-panel, something like 15 or 20 amp? The main in the sub-panel should not be tripping.

Yep! and it went right to the main breaker.
I said F it and threw it out in the trash and bought a new power supply. Works good now

[skrubol]

You might want to replace, or at least try to test the small breaker, if it wasn't tripping before or along with the 100A, something sounds wrong.

[RCaffin]

Perhaps hiring an experienced industrial electrician for half a day might be a good idea.

I will add that some breakers are designed to be fast-acting, while others are deliberately made slow acting, for motor starting.

Cheers
Roger

[skrubol]

I will add that some breakers are designed to be fast-acting, while others are deliberately made slow acting, for motor starting.

I'm not an expert at breakers, but I do know how they work, and I don't think any common 100A breaker should trip before any common 20A or lower breaker given the same load.
Circuit breakers have 2 trip mechanisms, thermal and magnetic. The thermal trip in most breakers is about the same for a given rating as far as I know. It will trip just a little bit above the rating of the breaker after a fairly long time (several seconds or minutes,) when the breaker is at a rated temperature.
The magnetic trip requires much higher current (up to 5x rating for B curve, 10x rating for C curve and 14x rating for D curve,) but it trips in under 1/10 second. It's possible the magnetic portion of the smaller breaker is non-functional or the breaker is somehow bypassed.

[Al_The_Man]

In my opinion, any piece of machinery such as this, however small, should have its own internal fusing or NFB of the correct value, this would normally have been included by any reputable machine manuf.'
However small.
Al.

[RCaffin]

Circuit breakers have 2 trip mechanisms, thermal and magnetic.
Not always. A lot of small breakers are thermal-only. The 7 A ones on the supply lines to each motor driver on my CNC are thermal-only. I don't want a fast sensitive trip on those supplies. Surge capacity is needed.

Cheers

[Al_The_Man]

Also modern motor O/L's are now mostly electronic, rather than the older thermal style.
Al.

[RCaffin]

Also modern motor O/L's are now mostly electronic, rather than the older thermal style.
Very true. I think my motor drivers can handle 10 A, but I have limited them below that. Well, belt and braces.

Cheers

[skrubol]

Right, but this is a breaker in a panel, not a DIN mount or overload in a motor driver isn't it?

[RCaffin]

I am not sure that it really matters whether the breaker is mounted in a panel or on a DIN rail - that's only a detail.

Yes, the motor driver does have a current limit set higher than the external breaker. That is deliberate. The breaker is a Tyco W38 Push-to-Reset thermal breaker.

Reality however is that 'normal' current load on the axis drivers is almost always <0.5 A. If the external breaker trips, it is because I goofed and the axis ran into an end stop.
This is where the difference matters. If I rely on the current limit in the motor it can sit there pouring 10 A into the motor until I hit the eStop - many seconds later. But if the axis does run into a hard limit, the external breaker will trip fairly quickly (1 second?), and everything is safe. Ah yes - the motor will also eStop around the same time - because it has exceeded the mandated current limit.

Like I said: belt and braces.

Cheers
Roger